Where: The Democratic National Convention in Philadelphia, Pennsylvania.

What: A royal blue a-line dress by Christian Siriano with cap sleeves and silver heels.

Why: The First Lady took to the stage with a rousing speech in support of Hillary Clinton on the first night of the Democratic National Convention. And, ever known for her impeccable taste — especially when it comes to American designers, making Siriano an evident choice — she wore a supreme look to match: an elegant knee-length dress with a strong shoulder and flattering front-seam detail, spicing it up with a pair of silver stilettos, softly waved hair, and a subtle smoky eye.